According to Wikipedia, any race can be considered an obstacle race if participants are required to overcome physical challenges that, by their very nature, are defined as obstacles. We’d need a huge amount of space here list all of the obstacles that fall under this umbrella, but here are a few of the most-often employed barriers: mud, trails, walls, water, fire, barbed wire and any combination of barriers that require one to test their strength, endurance, dexterity and mental acuity.